The mesa card looks interesting to me. The catch is, how is one going to go about doing spi and pulling the data into emc2? I assume everything would have to be bit banged, and is not taken care of in the fpga. It also says it has quadrature encoder interface, but once again, how is this handled? If this was handled with a accessible register, that would work pretty well.
On Mon, Feb 6, 2012 at 1:28 PM, Kirk Wallace <kwall...@wallacecompany.com>wrote: > On Mon, 2012-02-06 at 12:29 -0500, Erik Friesen wrote: > > I am not so sure about the parallel port and encoder idea though, the > > encoders I see are up to 1000 per rev, that requires a pretty fast base > > period to handle that, not? <2us ? > > In reference to my reply, I suggested that using the parallel port for > encoders, but only if the encoder pulse rate is similar to the step > rate. An FPGA PCI or parallel port board would be needed for decent > encoder rates. > > > I also am not very clear on emc2 capability to manage analog inputs, it > > seems easier to offload the deciding to an external mcu of some sort. > > Also, how would emc2 handle encoders with steppers? > > In the normal stepper configuration file, the position command and the > position feedback are software "shorted" together. > > core_stepper.hal > ~~~~~~~~~~~~~~~~~~~~~~~ > ... > 25 # connect position feedback from step generators > 26 # to motion module > 27 net Xpos-fb stepgen.0.position-fb => axis.0.motor-pos-fb > 28 net Ypos-fb stepgen.1.position-fb => axis.1.motor-pos-fb > 29 net Zpos-fb stepgen.2.position-fb => axis.2.motor-pos-fb > ... > ~~~~~~~~~~~~~~~~~~~~~~~ > > This is because when a step is sent out, it is assumed that the step > completes properly, and besides, a normal stepper system has no way of > providing feedback. I haven't worked on a stepper system with encoders, > but I think one replaces the above stepgen feedback with the encoder > output. > > This link indicates there is are example files somewhere?: > http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Steppers_With_Encoders > > For the cost, this may be a good analog trip indicator: > http://www.sparkfun.com/products/9147 > > The biggest problem might be in conditioning the analog signal to a 0 - > 5 Volt range. One could use the USB connection as is, or change the > program to just send out a one bit or watchdog signal. Being a > microprocessor, the trip conditions could be quite sophisticated. > -- > Kirk Wallace > http://www.wallacecompany.com/machine_shop/ > http://www.wallacecompany.com/E45/index.html > California, USA > > > > ------------------------------------------------------------------------------ > Try before you buy = See our experts in action! > The most comprehensive online learning library for Microsoft developers > is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, > Metro Style Apps, more. Free future releases when you subscribe now! > http://p.sf.net/sfu/learndevnow-dev2 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
